Raw vs. Boiled vs. Polymerized Linseed Oil Explained

By MWB-Team •  Updated: 05/19/23 • 

Linseed oil is a natural product made by pressing dried flax seeds, which is why it is also called flaxseed oil. As a finish, linseed oil has been used for many years to protect and maintain wood products. Linseed oil is also often used in varnishes, paints, and stains.

There are three different types of linseed oils. These are raw, boiled, and polymerized linseed oil. Each of these types of linseed oil is different and has its pros and cons.

What is Raw Linseed Oil?

Raw linseed oil is the oil extracted from the seeds of the flax plant without adding any other additives or ingredients. It is the purest form of linseed oil. It is like the kind used in nutritional supplements and as a leather conditioner.

As a wood finish, raw linseed oil is not very efficient. Depending on the weather and thickness during the application, it will take weeks or months to cure. Raw linseed oil is unappealing for finishing wood because of its long drying time.

Sunnyside Pure Raw Linseed Oil

If you want to revive your old and faded wood products, raw linseed oil is better. This natural wood protector can breathe new life into your wood and offer basic protection against elements. 

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The long drying time of raw linseed oil makes it great for treating willow bats. This is because the long drying time keeps the bats wet, locks in moisture, and holds the wood fibers together. This gives the bat a springy surface and better friction for better ball control.

What is Boiled Linseed Oil?

You can obtain boiled linseed oil, abbreviated as BLO, from raw linseed oil. Contrary to its name, boiled linseed oil is not obtained by boiling raw linseed oil. BLO is made by adding different metallic driers to raw linseed oil to make it more effective. These metallic driers include zinc, cobalt, or manganese. Boiled linseed oil can take a day to fully dry.

Linseed Oil on Beech Wood

Linseed Oil on Beech Wood

However, long ago, raw linseed oil used to be heated to incorporate driers. However, with time and technology, liquid driers do not require to be heated to mix properly. Although things have changed, the product is still called boiled linseed oil.

Apart from drying in a day, you can easily build up the coats of boiled linseed oil for a more durable and protective finish than raw linseed oil. However, because of the added driers, completely cure/dry BLO wood surfaces before using them.

What is Polymerized Linseed Oil?

Linseed oil cures slowly by absorbing oxygen. However, the curing process can be speeded up by heating the raw linseed oil in an oxygen-free environment at about 500 degrees Fahrenheit. Once raw linseed oil is heated for several days, it thickens, reducing drying time and increasing the viscosity. This process turns raw linseed oil into polymerized linseed oil.

When exposed to oxygen, polymerized linseed oil cures faster and turns into a hard and glossy oil finish. Unlike normal linseed oil, which is soft, polymerized linseed oil is harder when cured, and you can build up several coats for better protection.

Because polymerized linseed oil cures fast, It can be difficult to apply on larger surfaces. However, wipe it fast and apply thinner coats so you avoid tiny cracks in the film as it cures. For smaller surfaces, however, it works perfectly.

Raw vs. Boiled vs. Polymerized Linseed Oils

All three types of linseed oils we’ve discussed above can be used to finish wood. However, raw linseed oil will take longer to dry and thus is preferred by only some woodworkers. Boiled linseed oil will take a day to cure, while polymerized linseed oil will take 12 to 24 hours to dry.

Once dry and cured, all these three types of linseed oils are food-safe, and you can eat them. However, after the last coat, give the finish at least 30 days to cure in warm conditions. You can also smell the odor to check if the finish has cured. If the smell disappears, the surface is safe for food or mouth contact.


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